While researchers at the Manhattan Institute found that state test scores in English Language Arts had improved by 4 percentage points and math proficiency had jumped 6 percentage points, the gains were spread across the city.

The think tank examined scores of state math and English exams given to third through eighth graders in city schools between 2013 and 2015.

In poorer school districts, the number of students who scored proficient in English exams increased from 12% to 15% over that time period. But that still lagged behind wealthier districts, where 54% of student scored proficient, up from 49% in 2013, according to the report set to be released Thursday.

Over the same period, lower-income districts made gains in math scores with 17% proficient in 2015, compared to 13% in 2013. Those numbers are far below the proficiency rates of 54% and 61% in wealthier districts in 2013 and 2015.

The study provided some intriguing wrinkles.

In poorer school districts, the number of students who scored proficient in English exams increased — but not as much as those in wealthier school districts. (Scott Eells/Bloomberg)

"The most surprising finding was that Asian students in low-income school districts, despite facing a similar type of income-based achievement gap as other groups, are actually starting to close the gap with their high-income Asian peers in ELA proficiency and holding ground in math proficiency," said Alex Armlovich, a policy analyst for the Manhattan Institute who authored the report.

For example, Armlovich said, Asian students in all school districts, regardless of income, improved proficiency on the math test by about 5.4%.

A city Department of Education spokesman said the city is boosting programs to help close that gap.

"Student proficiency rates are up across the board and graduation rates are higher than they have ever been for black and Hispanic Students," said agency spokesman Harry Hartfield. "But we aren't satisfied until every student succeeds.

"That's why we're investing in initiatives like Pre-K for All, second grade literacy support and one-on-one academic support for middle school students."